Continuous enzymatic interesterification of milkfat with soybean oil produces a highly spreadable product rich in polyunsaturated fatty acids

The aim of this study was to tune the physical properties of milkfat by enzymatic interesterification with soybean oil in a continuous fluidized bed reactor (FBR) to obtain healthy interesterified fat blends having suitable texture properties for the food industry. The immobilized commercial non-regioselective Candida antarctica lipase (Novozym (R) 435) and sn1,3-regioselective Rhizopus oryzae lipase, immobilized in an organic-inorganic hybridmatrix of polysiloxane-polyvinyl alcohol, were used as biocatalysts in a FBR. The minimum value of the ascendant flow of the medium for allowing fluidization in the system was 3.13 mL.min(-1). The reaction was evaluated in terms of the interesterification yield (IY), consistency values and solid fat content (SFC). The IY values of 10.50 +/- 1.64% and of 5.70 +/- 1.46% were attained for Novozym (R) 435 and for immobilized R. oryzae lipase, respectively. The consistency of the initial 65: 35 milkfat/soybean oil mixture (1000 gf/cm(2)) decreased to 732.35 +/- 75.30 gf/cm(2) and to 478.02 +/- 71.80 gf/cm(2) in interesterified blends catalyzed by Novozym (R) 435 or by R. oryzae lipase, respectively. SFC was considered an inadequate parameter for following the interesterification of this blend formulation because the values were similar for initial and for interesterified blends. Free fatty acid levels of 1.5%, the non-notable deactivation of Novozym (R) 435 and a half-life of 190 h for R. oryzae lipase were observed during the operation time.